In electronic apparatuses such as liquid crystal display devices, there has been established a connecting technique of conductor patterns, which uses TAB (Tape Automated Bonding) and an anisotropic conductive film (hereinafter referred to as ACF) (see Non-patent Document 1, for instance).
In this technique, for example, an ACF is affixed to an electrode terminal of a liquid crystal panel and a chip connection terminal in a tape fragment on which a driver IC chip for the panel is mounted and then the panel electrode terminal and chip connection terminal undergo thermocompression bonding through the affixed ACF, whereby connection between these two terminals are accomplished. According to Non-patent Document 1, the panel electrode terminal is formed of aluminum or ITO (Indium Tin Oxide), while the chip connection terminal is formed of copper.
However, apart from the fact that forming a panel electrode terminal out of aluminum results in an advantage of reducing the electric resistivity of the terminal, such an aluminum terminal has a drawback that the terminal can be easily subject to corrosion such as rust. In addition, although forming a panel electrode terminal out of ITO results in an advantage of enhancing chemical stability of the terminal, i.e. resistance to corrosion such as rust, such an ITO terminal has a drawback that its resistivity is higher than those of typical metals having been used as suitable conductors.
The panel electrode terminal and chip connection terminal form their electrical connection by means of the ACF, in which the ACF itself has an insulating material as a parent matter and a multiple conductive particles dispersed and mixed in the material, and conducting paths are formed between the terminals by only some particles that are sandwiched between the terminals while being in physically contact with the terminals, among all the conductive particles. However, since dispersiveness of the conductive particles in the insulating material is not strictly uniform and varies, positions of the conductive particles in contact with the terminals are also uneven. In other words, there is a possibility that short conducting paths are formed between some twos of the terminals, while long conducting paths are formed between other twos of the terminals. The electrical resistances of the terminal connection portions thereby can vary, and despite signals with the same levels being transmitted from the chip side, the panel side may receive signals with different levels and be brought into different driving states.
[Non-patent Document 1]
Yasoji Suzuki, ‘Introduction to Liquid Crystal Display Engineering’, NIKKAN KOGYO SHINBUN, LTD, Nov. 20, 1998, First edition, pages 42 to 46